Zinc alloy

ABSTRACT

A TERNARY ALLOY OF HIGH-PURITY ZINC, NICKEL AND CHROMIUM HAVINGG HIGH CREEP RESISTANCE AND OTHER GOOD MECHANICAL PROPERTIES FOR USE AS BANDS, STRIPS, SHEETS WIRE OR ROD WHICH CONTAINS CR AND NI WIITHIN THE AREA ABCD OF THE ZINC-CHROMIUM-NICKEL COMPOSITION DIAGRAM SHOWN IN THE DRAWING WHEREIN A CORRESPONDS TO 0.05% BY WEIGHT CHROMIUM AND 0.05% BY WEIGHT NICKEL (BALANCE HIGHPURITY ZINC), B CORRESPONDS TO 0.20% BY WEIGHT CHOMIUM AND 0.05% BY WEIGHT NICKEL (BALANCE HIGH-PURITY ZINC), C CORRESPONDING TO 0.05% BY WEIGHT CHROMIUM AND 0.20% VBY WEIGHT NECKEL (BALANCE HIGH-PURITY ZINC), AND D CORRESPONDS TO 0.45% BY WEIGHT TO 0.55% BY WEIGHT CHRONIUM AND 0.45% BY WEIGHT TO 0.55% BY WEIGHT NICKEL (BBALANNCE HIGH-PURITY ZONC). UP TO 1.7% BY WEIGHT OF ZINC MAY BE REPLACED BY AN EQUAL QUANTITY OF COPPER.

E. PELZEL Z INC ALLOY June 19, 1973 Filed Oct. 9, 1970 Erich 4Pes/zel Y mentor.

4United States Patent O 3,740,214 ZINC ALLOY Erich Pelze, Puchheim, near Munich, Germany, assignor to Stolberger Zink AG fur Bergbau und Huttenbetrieb, Aachen, Germany Filed Oct. 9, 1970, Ser. No. 79,533 Claims priority, application Germany, Oct. 25, 1969, P 19 53 783.8 Int. Cl. C22c 17/00 U.S. Cl. 755-178 R 5 Claims ABSTRACT F THE DISCLUSURE A -ternary alloy of high-purity zinc, nickel and chromium having high creep resistance and other good mechanical properties for use as bands, strips, sheets, wire or rod which contains Cr and Ni within the area ABCD of the zinc-chromium-nickel composition diagram shown in the drawing wherein A corresponds to 0.05% by weight chromium and 0.05% fby weight nickel (balance highpurity zinc), B corresponds to 0.20% by weight chomium and 0.05 by weight nickel (balance high-purity zinc), C corresponding to 0.05% by weight chromium and 0.20% by Weight nickel (balance high-purity zinc), and D corresponds to 0.45 Iby weight to 0.55% by weight chromium and 0.45 by weight to 0.55% by weight nickel (balance high-purity zinc). Up to 1.7% by weight of zinc may be replaced by an equal quantity of copper.

My present invention relates to zinc alloys with improved mechanical properties and, more particularly, to a ternary alloy of zinc, chromium and nickel with improved creep resistance and strength properties.

Numerous zinc alloys have been proposed heretofore for the production of zinc bands, strips, sheet, wire, rods, proles and bars, for construction and other uses, since elemental zinc, free from alloying ingredients, has poor mechanical properties in many important respects. For example, zinc is prone to creep, i.e. deform under the static load, even at ambient temperatures. Consequently, eliorts have been made to increase the tear strength, the ductility and the tensile strength of zinc bodies, while also reducing the tendency to creep. While a review of all of the hitherto disclosed alloys which purport to improve the properties of zinc bodies may only result in confusion, special attention should be given to earlier proposals whereby copper and chromium, copper and titanium, manganese, iron and other alloying metals have been used in varying quantities to modify the physical properties of i zinc. For the most part, the prior-art attempts have been unsuccessful in yielding alloys which successfully may be employed in the construction trades, which are sutiiciently ductile and creep resistant to be rolled into strips, sheet, bands and the like or to be drawn or rolled into wire and rod, and whichyet have the necessary creep resistance. As a matter of fact, it has been found that the crystallography of zinc and zinc alloys is highly complex and that the user of Aalloying ingredients which themselves appear to improve the creep resistance of zinc, when utilized in combination, does not always provide similar etfects or may even destroy some of the improvement already gained. There appears, therefore, to be a significant dependency upon the manner in which the zinc and alloy crystals form in the zinc body, i.e. upon the nature of the eutectoids and the solid solutions formed.

It is, therefore the principal object of the present invention to provide an improved zinc alloy whereby disadvantages of the prior systems are avoided.

It is another object of this invention to provide a zinc alloy particularly suitable for rolling into strip, bands, sheets and the like.

3,740,214 Patented June 19, 1973 It is another object of this invention to provide an im proved zinc alloy particularly suitable for drawing into wire and rod.

Still further, it is an object of the invention to provide zinc alloy bodies with high. creep resistance and tensile strength.

These objects and others, which. will become apparent hereinafter, are attained in accordance with the present invention, with zinc alloys within a well-defined composi tion range in the ternary composition diagram of highpurity zinc, nickel and chromium. More particularly, we have discovered that there exists in this ternary composition diagram (see the drawing), a region dened by the points A-B which provides the surprising result of low creep and high mechanical strength and ductility.

In the discussion below with respect to the composition, reference is made to high-purity zinc. To define this term, it is best to recall that zinc is generally available in a number of grades such as selected, brass special," intermediate, high-grade and special high-grade. The latter two grades are defined for the purposes of the present invention as high-purity zinc. In other words, highpurity `Zinc is zinc which contains a maximum of 0.07% by weight lead, 0.02% by weight iron and 0.07% by weight cadmium. The sum of the lead, iron and cadmium will not exceed 0.10% by weight. Preferably, however, the high-purity zinc is the special highegrade zinc as delined by ASTM speciiication B 6-49 and contains at most 0.006% by weight lead, 0.005% by weight iron and 0.004% by Weight cadmium (total lead, iron and cadmium being at most 0.01% by weight).

` The area of the zinc/ chromium/ nickel ternary composition diagram is the polygon dened by the vertices A, B, C and D wherein:

0.05 by weight chromium and 0.05 by weight nickel, balance high purity zinc; B:

0.20% by weight chromium and 0.05% by weight nickel, balance high-purity zinc; C:

0.05 by Weight chromium 0.20% by weight nickel balance high-purity Zinc; D:

0.45% to 0.55% by weight chromium and 0.45% to 0.55% by weight nickel balance high-purity zinc.

Preferably:

0.50% by weight chromium and 0.50% by Weight nickel balance high-purity zinc.

The points A, B, C and D dene lines which constitute phase boundaries and have been observed empirically to define the limits of the operable alloy. The eutectoid of this composition is 0.12% by weight chromium and 0.18% by weight nickel (balance high-purity zinc).

Surprisingly, I have also found that up to 1.7% of ythe high-purity zinc may be replaced by copper, this amount ibeing the maximum of copper which forms a solid solution in Zinc without producing any heterogeneities, lattice or crystalline discontinuities or additional phase boundaries.

In the aboveeidenti-ed eutectic concentration range, the ternary alloy of high-purity zinc, nickel and chromium, in spite of its increasing heterogeneity and increasing solidification interval (as the concentration changes in the direction of point D) grows more line-grained, so that the tensile strength increases while the ductility remains. Only when the concentration exceeds that of the point D, i.e. When either 0.5 weight-percent nickel or chromium 4 Examples 6-10 were carried out by extruding the alloy from a molten state at 450 C. to round bars'of 150 mm. diameter. The bars were then hot-pressed at 250 C. and drawn cold to Wire with a diameter of 1.5 mm. In Example 8, 1.7% of the zinc was replaced by copper is exceeded in the composition does this effect cease.

While at the.outset, it may appear that the range of interest and the tensile strength of the wire was thereby increased in accordance with the present invention is relatively to 50 kp./mm.2.

broad, it should be noted that it constitutes a small frac- The products according to the present invention were of tion only of the range of ternary compositions between increased hardness and tensile strength and high elongata- 0.05% and 0.5% by weight chromium and between 10 bility.

0.05% and 0.5 by weight nickel. I claim:

At the conclusion of primary crystallization, the lattice 1. A ternary zinc/ nickel/ chromium alloy consisting structure appears to be a pseudoeutectoid in the form essentially of Oto 1.7% by weight copper, and nickel and of fine crystals and aV matrix phase of the ternary eutectic. chromium in amounts within the area ABCD of the draw- The zone of interest, according to the present invention, ing, balance high-purity zinc, wherein can be considered tobe subdivided into several subzones as will be apparent hereinafter. The point E described 0.05% by Weight chromium and below is, of course, the eutectic point. Consequently, the 0.05% by weight nickel; region ABEC, designated a, solidifies `as -a fine-grained B: crystal structure provides the fatigue strength and tensile 0.20% by Weight chromium and strength, in major part, of the alloy. 'Ihe ternary alloy 0.05% by weight nickel; developing in this range has a tensile strength up to 30 C: kp./mm.2 and is advantageously rolled into bands, sheets 0.05% by weight chromium and and strips. This ternary alloy has a primary segregation `0.20% by weight nickel; and of zinc grains in the eutectoid matrix. D=

In the phase zone defined by the points C, E and D, 0.45% to 0.55% by weight chromium and the primary precipitate is nickel grains which provide a 0.45% to 0.55 by Weight nickel. fine-grain structure; the latter, as noted, affords high 2. The alloy defined in claim 1 wherein ductility in spite of the increasing solidification interval D= and the alloy has been found to be suitable for cold de- 0.50% by weight chromium and formation. In the phase zone fy, defined by the points B, E 0.50% by weight nickel. and D, the primary crystals are of chromium with a fine- 3. The alloy defined in claim 1 having Ia ternary grain structure and permit, in the presence of copper as eutectic point of noted, tensile strength up to 50 kp./mm.2 and tensile 0.12% by weight chromium and strength above 50 lkp./mm.2 in copper-containing alloys 35 0.18% by Weight nickel. according to the invention along the phase boundary DE. 4. A sheet zinc alloy rolled from the composition de- The ternary alloy in the zone or ridge on either side of fined in claim 1 and within the area ABCE of the drawthe line DE, represented as the region BECD, therefore, ing. has been found to be particularly suitable for the pro- 5. Wire drawn from the composition defined in claim 1 duction of wire by drawing. and within the area ADCE of the drawing.

TABLE Fatigue Elongstrength Percent by Weight Tensile ation creep re- Example strength (percent) sistance No. N1 Cr Cu Zn (kn/nun!) (to brake) (kn/mm!) Use 0.05 0.05 Remainder.. 18 70 6 Band, strip, sheet. 0.10 0.10 19 70 6 D0. 0.15 0.15 20 80 7 Do. 0.25 0.15 23 80 8 Do. 0.25 0-.15 30 65 9 Do. 0.25 0.20 25 60 9 Wire rod 0. a5 0.30 35 50 10 15o. 0.35 0. 30 50 40 10 D0. 0.40 0. 4o 15 11 Do. 0.50 0.50 10 12 D0.

The above examples illustrate the invention, the References Cited table giving the composition, tensile strength, elongation UNITED STATES PATENTS to break, fatigue strength or creep resistance and use of ten compositions in accordance with the present invention. 3527601 9/1970 Forster 75178 R.

The alloys of Examples 1-5 are cast at 450 C. into 2011987 8/1935 Talnton et al 75-"178 R blocks with a thickness of 80 mm. After solidification, 60 1506772 9/1924 Pack 75-178 R the blocks are rolled into ductile high-elongatability FOREIGN PATENTS sheets or bands at a temperature of 250 C. in a number 1,319,535 1/1963 ,France 75 173 R of rolling steps to a thickness of 10 mm. (hot-rolling), thereafter the sheets are rolled in several passes to a L. DEWAYNE RUTLEDGE, Primary Examiner thickness of 1 mm' (cold`roumg)' 65 L. WEISE, Assistant Examiner In lExample 5, 1.00% of the zinc is replaced by copper, thereby increasing lthe tensile strength to 30 kp./mm.2 without affecting its elongation to break.

U.S. Cl. X.R. --178 C UNTTED STATES PATENT OTTTCE CERTIFICATE 0F CGRBECTION Patent No. Q 7LILO,21) Dated June 19, 1973 Inventor-(S) P91281 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Colmn l, line 3, "Erich Pelze" should read Signed and sealed this 26th day of February 197L|.

(SEAL) Attest:

EDWARDl M.FLETCHER,JR. C. MARSHALL DANN m Attesting Officer T Commissioner of Patents FORM P0'1050 (1069) uscoMM-Dc coen-puo U.S, GOVERNMENT FRINTING OFFICE l," 0-'35-33. 

